Imagine that you wanted to estimate the price elasticity of demand for cigarettes in the United States. One approach might be to take advantage of the differences in prices across states due to...

Imagine that you wanted to estimate the price elasticity of demand for cigarettes in the United States. One approach might be to take advantage of the differences in prices across states due to differences in cigarette taxes. For example, you might regress per capita consumption of cigarettes in each state on the retail price of cigarettes in that state. What other variables might you want to include in your model?